Age-related osteoporotic fracture is largely due to the universal reduction in bone strength that occurs with age. Bone density is the main component of bone strength. About 80% of variance in bone density in whites is due to heritable factors that appear to be regulated by relatively few genes.Blacks have higher bone density and lower bone turnover than whites, but heritability and genetic linkage of these phenotypes have not been studied. Overall goal is to establish that heritable factors account for a similar proportion of variance in bone strength in blacks and whites, and to identify genetic markers for bone strength and bone turnover.